Semiconductor device and method for monolithically integrated power device and control logic

ABSTRACT

A monolithic semiconductor device has a substrate with a power region and control region. The substrate can be a silicon-on-insulator substrate. An opening is formed in the power region and extends partially through the substrate. A semiconductor material is formed within the opening. A power semiconductor device, such as a vertical power transistor, is formed within the semiconductor material. A control logic circuit is formed in the control region. A first isolation trench is formed in the power region to isolate the power semiconductor device and control logic circuit. A second isolation trench is formed in the control region to isolate a first control logic circuit from a second control logic circuit. An interconnect structure is formed over the power region and control region to provide electrical interconnect between the control logic circuit and power semiconductor device. A termination trench is formed in the power region.

CLAIM TO DOMESTIC PRIORITY

The present application claims the benefit of U.S. ProvisionalApplication No. 62/363,449, filed Jul. 18, 2016, by Jefferson W. HALLand Gordon M. GRIVNA, which application is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates in general to semiconductor devices and,more particularly, to a semiconductor device and method for amonolithically integrated power device and control logic.

BACKGROUND

A semiconductor wafer or substrate can be made with a variety of basesubstrate materials, such as silicon (Si), germanium, aluminumphosphide, aluminum arsenide, gallium arsenide (GaAs), gallium nitride(GaN), aluminum gallium nitride over gallium nitride (AlGaN/GaN), indiumphosphide, silicon carbide (SiC), or other bulk material for structuralsupport. A plurality of semiconductor die is formed on the waferseparated by a non-active, inter-die substrate area or saw street. Thesaw street provides cutting areas to singulate the semiconductor waferinto individual semiconductor die.

A power metal oxide semiconductor field effect transistor (MOSFET) iscommonly used to switch relatively large currents. Many applicationsrequire several power MOSFETs, for example, to independently controlelectrical current in different loads. For instance, an automobile mayrequire separate power MOSFETs to switch current through actuators thatroll windows up and down, adjust rear-view mirrors, and adjust theposition of car seats. Power MOSFETs may also be used to switchelectrical current to heating elements within windows and mirrors, or aspart of a switch-mode power supply to convert battery voltage to anothervoltage. In such applications, the electrical currents can be relativelyhigh, leading to a need for high density, low loss switches resulting inhigh efficiency.

Each power device used to switch an electrical current requires controllogic to determine when to turn the switch on and off. Commonly, thecontrol logic for each power device is located in a control logicsemiconductor package, and each of the power devices are separatelypackaged and placed on a common printed circuit board (PCB) or remotelyfrom the control logic package. The plurality of separate semiconductorpackages adds cost and consumes PCB area.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1a-1b illustrate a semiconductor substrate with a plurality ofsemiconductor die separated by a saw street;

FIGS. 2a-2t illustrate a process of forming power regions and controlregions in an SOI substrate;

FIGS. 3a-3h illustrate a process of forming vertical gate structures inthe power regions for the power MOSFET;

FIGS. 4a-4f illustrate a process of forming control logic in the controlregion for the power MOSFET;

FIG. 5 illustrates the semiconductor device in a leadframe with drainsensing;

FIGS. 6a-6e illustrate forming power regions and control regions in anon-SOI substrate; and

FIGS. 7a-7b illustrate the semiconductor device in a diode bridgeconfiguration.

DETAILED DESCRIPTION OF THE DRAWINGS

The following describes one or more embodiments with reference to thefigures, in which like numerals represent the same or similar elements.While the figures are described in terms of the best mode for achievingcertain objectives, the description is intended to cover alternatives,modifications, and equivalents as may be included within the spirit andscope of the disclosure. The term “semiconductor die” as used hereinrefers to both the singular and plural form of the words, andaccordingly, can refer to both a single semiconductor device andmultiple semiconductor devices.

FIG. 1a shows a semiconductor wafer or substrate 100 with a basesubstrate material 102, such as Si, germanium, aluminum phosphide,aluminum arsenide, GaAs, GaN, AlGaN/GaN, indium phosphide, SiC, or otherbulk material for structural support. Semiconductor substrate 100 has awidth or diameter of 100-450 millimeters (mm) and thickness of about700-800 micrometers (μm). A plurality of semiconductor die 104 is formedon substrate 100 separated by a non-active, inter-die substrate area orsaw street 106. Saw street 106 provides cutting areas to singulatesemiconductor substrate 100 into individual semiconductor die 104.

FIG. 1b shows a cross-sectional view of a portion of semiconductorsubstrate 100. Each semiconductor die 104 includes a back surface 108and active surface or region 110 containing analog or digital circuitsimplemented as active devices, passive devices, conductive layers, anddielectric layers formed within the die and electrically interconnectedaccording to the electrical design and function of the die. For example,the circuit may include one or more transistors, diodes, and othercircuit elements formed within active surface or region 110 to implementanalog circuits or digital circuits. Semiconductor die 104 may alsocontain a power device, control logic, digital signal processor (DSP),microcontroller, ASIC, standard logic, amplifiers, clock management,memory, interface circuit, optoelectronics, and other signal processingcircuits. Semiconductor die 104 may also contain integrated passivedevices (IPDs), such as inductors, capacitors, and resistors, for RFsignal processing. In particular, semiconductor die 104 contains one ormore monolithically integrated vertically oriented power devices andassociated control logic with relatively high density.

The following figures illustrate manufacturing high density powerMOSFETs on a common die with control logic for switching the powerMOSFETs. In FIG. 2a , silicon-on-insulator (SOI) substrate 120 includesa base substrate or handle wafer 122. Base substrate 122 is relativelyheavily doped (N++) with donor dopant atoms. Donor dopant atoms providean extra electron to the silicon lattice to provide a negative or N-typeregion. Acceptor dopant atoms create an electron hole in the siliconlattice to provide a positive or P-type region.

An N-type epitaxial (EPI) layer 124 can be grown on base substrate 122.Wafer 126 is relatively light doped with donor atoms. Wafer 126 and basesubstrate 122 each have an oxide layer grown on surfaces of the wafers.The oxide layers on wafer 126 and base substrate 122 are cleaned andatomically bonded to form buried oxide (BOX) layer 128. Base substrate122 with EPI layer 124 bonded to wafer 126 through BOX layer 128 formsSOI substrate 120. In some embodiments, where a high voltage powerMOSFET is formed, EPI layer 124 can be grown to a greater thickness. SOIsubstrate 120 de-couples the drain regions from the control logicregions.

In FIG. 2b , an oxide layer 130 is formed over wafer 126 of SOIsubstrate 120. Nitride layer 132 is formed over oxide layer 130. Aportion of wafer 126, BOX layer 128, oxide layer 130, and nitride layer132 is removed in power regions 140 a and 140 b, as shown in FIG. 2c ,to form openings 134 extending partially through SOI substrate 120 tocontain later-formed power MOSFETs. The layers are removed by laserdirect ablation (LDA), plasma etching, or combination of etchingprocess. Wafer 126, BOX layer 128, oxide layer 130, and nitride layer132 remain within control region 144, as isolation for later formedcontrol logic. FIG. 2d illustrates a plan view of SOI substrate 120 withpower regions 140 a and 140 b separated by control region 144. Controlregion 144 can be centrally located with respect to power regions 140 aand 140 b, or disposed in any other location on semiconductor die 104.For example, control region 144 can be disposed at one or more locationsaround a perimeter of semiconductor die 104 and power regions 140 a and140 b disposed central to control region.

FIG. 2e illustrates a smaller portion 146 of SOI substrate 120 focusedaround boundary 148 between control region 144, where CMOS control logicis formed, and power region 140 a or 140 b, where vertical power MOSFETsare formed. While the disclosed examples illustrate the power devices asbeing vertical power MOSFETs, other power devices can be formed in powerregions 140 a and 140 b. Semiconductor die 104 may have multiple powerdevices formed monolithically, each having accompanying control logic.

In FIG. 2f , an oxide layer 150 is formed to isolate sidewalls 152 ofwafer 126 and BOX layer 128. Oxide layer 150 extends over EPI layer 124in power regions 140 a and 140 b. FIG. 2f and subsequent figurescontinue to show the smaller portion 146 of SOI substrate 120 focusedaround boundary 148 between control region 144 and power region 140 b,similar to FIG. 2e . In FIG. 2g , oxide layer 150 across EPI layer 124in power regions 140 a and 140 b is removed by plasma etching or otheretching process, leaving oxide layer 150 oriented vertically onsidewalls 152 of wafer 126 and BOX layer 128. Nitride layer 132 isremoved by plasma etching or other etching process to expose oxide layer130. FIG. 2h shows a plan view of SOI substrate 120 with power regions140 a and 140 b and the remaining oxide layer 130 over control region144.

In FIG. 2i , a selective EPI growth is performed on EPI layer 124 of SOIsubstrate 120 to form EPI layer 160 within power regions 140 a and 140b. Region 162 at the boundary between EPI layer 160 and oxide layer 150typically contains defects in the atomic lattice. The selective EPIgrowth provides silicon with near perfect atomic lattice up from EPIlayer 124, while leaving a relatively small region 162 of defectsproximate to oxide layer 150. In some embodiments, EPI layer 160 has adifferent dopant atom concentration than wafer 126. The disclosedmanufacturing process provides the flexibility of having various dopantconcentrations, types of dopant, or dopant thicknesses between themultiple control region 144 and power regions 140 a and 140 b.Accordingly, each power device can be formed with a different dopingprofile by separate selective EPI growth steps using multiple masks.FIG. 2j shows a plan view of SOI substrate 120 with EPI layer 160 inpower regions 140 a and 140 b.

In FIG. 2k , pad oxide 164 is formed over EPI layer 160 in power regions140 a and 140 b. In FIG. 2l , isolation trench 166 is formed aroundpower regions 140 a and 140 b including through region 162 to removeimperfections where EPI layer 160 meets oxide layer 150. Isolationtrench 166 has a ring, rectangular, or otherwise enclosing shape andextends through EPI layer 160 and partially into EPI layer 124. An oxidelayer 168 is conformally applied over EPI layer 160 in power regions 140a and 140 b and over oxide layer 130 in control region 144 and furtheron the sidewall of isolation trench 166. A polysilicon material 170 canbe deposited in a remaining portion of isolation trench 166 over oxidelayer 168 to form isolation structure 172 in power regions 140 a and 140b. Alternatively, isolation trench 166 is filled with oxide layer 168.Isolation structure 172 isolates power devices in power regions 140 aand 140 b from the control logic in control region 144.

An isolation trench 174 is formed in control region 144 to isolatecontrol region 144 a from control region 144 b. Isolation trenches 166and 174 can be formed by LDA, plasma etching, or other etching process.Isolation trench 174 has a ring, rectangular, or otherwise enclosingshape and extends through wafer 126 to BOX layer 128 in control region144. Oxide layer 168 is conformally applied on the sidewall of isolationtrench 174. Polysilicon material 170 can be deposited in a remainingportion of isolation trench 174 over oxide layer 168 to form isolationstructure 175 in control region 144. Alternatively, isolation trench 174is filled with oxide layer 168 or other dielectric. Isolation trench 174isolates control logic between multiple power devices in control regions144 a and 144 b. FIG. 2m shows a plan view of SOI substrate 120 withisolation trenches 166 and 174 and oxide layer 168.

Additional isolation trenches 166 can be used with more power devicesmonolithically integrated on a common SOI substrate 120. In someembodiments, wider isolation regions or multiple concentric trench rings166 a and 166 b in FIGS. 2n and 2o are formed where additional isolationis desired, e.g., for high voltage termination.

FIG. 2p show an alternate embodiment with isolation trench 166 formedsimilar to FIG. 2l followed by a deeper oxide spacer etch extending intobase substrate 122. Likewise, isolation trench 174 is formed similar toFIG. 2l followed by a deeper oxide spacer etch extending into basesubstrate EPI layer 124. The oxide spacer etch is filled withphosphorous doped polysilicon 176 to create a conductive channel fromthe top surface of SOI substrate 120 to base substrate 122 in powerregions 140 a and 140 b, and further create a conductive channel fromthe top surface of SOI substrate 120 to EPI layer 124 in control region144 a and 144 b. Polysilicon 176 extending into base substrate 122 andEPI layer 124 provides a top surface connection to the power devicesubstrates that can be routed to control logic in control region 144using metal routing. Polysilicon 176 allows control logic to sense thedrain voltage of power devices in power regions 140 a and 140 b. Forembodiments with higher drain voltages being sensed by control logic,additional trenches around polysilicon 176 may be formed.

Returning to FIG. 2l , vertical gate trenches 180 are formed acrosspower regions 140 a and 140 b, for example, in a parallel arrangement. Awidth W₁ of gate trenches 180 is about 0.3 μm. A width W₂ between gatetrenches 180 is about 0.5 μm. A high voltage termination trench 182 isformed around gate trenches 180 of power regions 140 a and 140 b. FIG.2r shows a plan view of SOI substrate 120 with gate trenches 180 andtermination trench 182 around the gate trenches.

FIGS. 3a-3h illustrate further detail of forming vertical gatestructures of the power MOSFET in gate trenches 180 and high voltagetermination trench 182 in power regions 140 a and 140 b. In FIG. 3a ,gate oxide layer 184 is conformally applied over EPI layer 160 and intogate trenches 180 and termination trench 182. Nitride layer 186 isconformally applied over gate oxide layer 184 on EPI layer 160 and intogate trenches 180 and termination trench 182. A width W₃ of the openingin gate trench 180 is about 0.16 μm after forming nitride layer 186. InFIG. 3b , an oxide layer 188 is conformally applied into gate trenches180 and termination trench 182 over nitride layer 186. Phosphorous dopedpolysilicon 190 is deposited into gate trenches 180 to form field platesfor the power MOSFET. A width W₄ of phosphorous doped polysilicon 190 ingate trenches 180 is about 0.1 μm. Phosphorous doped polysilicon 190 isalso deposited into termination trench 182.

In FIG. 3c , a portion of polysilicon 190 in gate trenches 180 isremoved by LDA, plasma etching, or other etching process to a depth D1of 1.0 μm or less. A portion of polysilicon 190 in termination trench182 is also removed by LDA, plasma etching, or other etching process. InFIG. 3d , a portion of oxide layer 188 is removed wet etching or otheretching process down below polysilicon 190. An end portion ofpolysilicon 190 extends above the remaining oxide layer 188 in gatetrenches 180 and termination trench 182 after the etching process. InFIG. 3e , oxide layer 192 is formed over the exposed end portion ofpolysilicon 190 in gate trenches 180 and termination trench 182. In FIG.3f , oxide layer 194 is formed in gate trenches 180 and terminationtrench 182 to smooth the oxide over polysilicon 190. In FIG. 3g , theexposed portion of nitride layer 186 is removed by wet etching or otheretching techniques. A high temperature oxide (HTO) layer 196 is formedover oxide layer 192, oxide layer 194, and gate oxide layer 184. In FIG.3h , phosphorous doped polysilicon 200 is deposited to fill gatetrenches 100 as vertical gate structures 202 of the power MOSFET.Surface 204 undergoes chemical-mechanical planarization or other removaltechnique.

FIG. 2s shows SOI substrate 120 following formation of vertical gatestructures 202 in FIGS. 3a-3h for the power MOSFET in power regions 140a and 140 b. FIG. 2t shows a plan view of SOI substrate 120 withvertical gate structures 202 in power regions 140 a and 140 b. The powerMOSFET is a high density vertical power semiconductor device.

FIGS. 4a-4f show a process of forming complementary metal oxidesemiconductor (CMOS) control logic in control regions 144 a and 144 b,and the doped regions of the power MOSFET in power regions 140 a and 140b. SOI substrate 120 is oriented to show further detail of controlregions 144 a and 144 b. In FIG. 4a , P-type well region 210 is formedin control region 144 b of wafer 126, and P-type well region 212 isformed in control region 144 a of wafer 126. One or more transistors areformed in wafer 126, including P-well regions 210 and 212, as controllogic circuits 213 a and 213 b to achieve the requisite functionality incontrol of the power MOSFETs in power regions 140 a and 140 b. In someembodiments, other CMOS, bipolar, or DMOS analog and mixed signaltransistors, as well as other discrete devices, are used to form controllogic in control regions 144 a and 144 b of wafer 126.

A P-type region 214 is formed between gate structures 202 in powerregions 140 a and 140 b as the channel region of the power MOSFETs. Insome embodiments, a charge balanced superjunction can be used. FIG. 4bshows a plan view of SOI substrate 120 with P-type well region 210formed in control region 144 b of wafer 126, P-type well region 212formed in control region 144 a for various control logic transistors,and P-type region 214 is formed between gate structures 202 in powerregions 140 a and 140 b.

In FIG. 4c , an interconnect structure 220 is formed over SOI substrate120. Interconnect structure 220 includes conductive vias 222 formedthrough insulating layer 224 to connect to control logic transistorsformed in control regions 144 a and 144 b. Conductive vias 222 furtherconnect to P-type region 214 and gate structures 202 in power regions140 a and 140 b. Conductive layer 226 is formed over insulating layer224 and conductive vias 222. Insulating layer 228 is formed overconductive layers 226 and insulating layer 224. Conductive layer 226 andconductive vias 222 provide electrical interconnect for control circuits213 a and 213 b to control the power devices in control regions 140 aand 140 b. Additional insulating layers like 230, conductive layer 226,and conductive via 232 can be formed for electrical interconnect androuting.

Conductive plug 234 operates as a front-side source contact throughconductive vias 222 to the power MOSFET in power regions 140 a and 140 band is configured for a leadframe to be coupled to the source of thepower MOSFET by a clip, bond wire, or other appropriate mechanism.Conductive layer 236 routes electrical signals from the control logic incontrol regions 144 a and 144 b to contact pads for connection to theleadframe by wire bonding or other appropriate connection method.Insulating layer or encapsulant 238 is formed over conductive layer 236and conductive plug 234 for environmental protection and structuralintegrity. An opening is etched through insulating layer 238 to exposeconductive plug 234 and contact pads of conductive layer 236 forsubsequent interconnect.

In FIG. 4d , SOI substrate 120 is shown inverted to form trench 240 withbackside etching through base substrate 122 and EPI layer 124. In oneembodiment, plasma etching is used to form trench 240. Trench 240provides lateral isolation between the plurality of power regions 140and control regions 144 on SOI substrate 120. Trench 240 separates basesubstrate 122 into a portion 122 a connected to the drain of a powerMOSFET formed in power region 140 a, and a portion 122 b connected tothe drain of a power MOSFET formed in power region 140 b. Accordingly,trench 240 provides isolation of the multiple drain regions onsemiconductor die 104. EPI layer 124 is likewise separated into portions124 a and 124 b. In some embodiments, an additional trench like 240 isformed between power region 140 a and control region 144, such that theportion 122 a of base substrate 122 is isolated from the power MOSFET inpower region 140 a and sits as an island over control region 144. Trench240 can extend laterally to trench 166 such that base substrate 122 andEPI layer 124 remain directly over power region 140, and are completelyremoved over control region 144. However, base substrate 122 and EPIlayer 124 remain extending over control region 144 to improve diestrength and planarity of the wafer backside. Base substrate 122extending over control region 144 also allows conductive vias to beformed through BOX layer 128 to couple the control logic circuitry tothe respective power MOSFETs.

In FIG. 4e , an insulating or passivation layer 242 is formed over basesubstrate 122, including into trench 240. Insulating layer 242 includesopenings over power regions 140 for the formation of drain contacts 244.FIG. 4f illustrates a plan view of semiconductor device 250 afterformation of passivation layer 242 and drain contacts 244. Semiconductordevice 250 includes two monolithically integrated vertical power MOSFETsformed in power regions 140 a and 140 b, and separately isolated analog,digital, or mixed signal control logic formed in control region 144 foreach of the vertical power MOSFET. Each of the power devices can operateat a different voltage by varying the thickness of the EPI layers forthe particular power devices, as well as varying the trench depth of thepower devices.

Trench 240 surrounds power regions 140 a and 140 b and creates a lateralseparation between portion 122 a and portion 122 b of base substrate122. Trench 240 electrically isolates the drain terminal of a powerMOSFET in power region 140 a from the drain terminal of a power MOSFETin power region 140 b. Vertical isolation between the control logic andpower device drain terminals is provided by buried oxide layer 128.Portion 122 a of base substrate 122 includes a branch that extends undercontrol region 144 a, and portion 122 b extends under control region 144b, so that control logic is able to contact the drain of power MOSFETsformed in power region 140 a using a conductive via through BOX layer128. If a bonding wire is used to couple control region 144 to the drainleadframe contacts, or if no backside connection is required, basesubstrate 122 may be completely removed under control region 144.Removing additional material of base substrate 122 and EPI layer 124under control region 144, or electrically isolating the material fromall power devices, reduces interference in the control logic caused bythe high voltage drain contacts.

Semiconductor device 250 is disposed on a leadframe and attached bymetallurgical bonding between drain contacts 244 and the leadframe. Aclip from the leadframe to source contacts 234 provides an externalsource contact for each of the vertical power MOSFETs. Likewise, draincontact 244 can be routed by bond wire or clip to the top surface ofsemiconductor device 250, e.g. for drain sensing. Bonding wires are usedto couple other leadframe contacts to terminals of control region 144for I/O of signals necessary for control of power MOSFETs formed inpower regions 140 a and 140 b. Semiconductor device 250 is encapsulatedelectrical interconnect and singulated to finish the package.

Semiconductor device 250 combines one or more power devices and controllogic fully isolated (source, drain, and gate of power MOSFET andcontrol logic) in an integrated monolithic semiconductor package usingan SOI substrate or non-SOI substrate. The power devices and controllogic can be lateral or high density vertical trench-based semiconductordevices with vertical conduction path from active surface 110 to backsurface 108 in semiconductor die 102. Conductive layers 226 and 236provide electrical interconnect on a first major surface for controllogic circuits 213 a and 213 b. Conductive layer 234 provides electricalinterconnect on the first major surface for the power MOSFET, e.g.source connection. Conductive layer 244 provides electrical interconnecton a second major surface for the power MOSFET, e.g. drain connection.Semiconductor device 250 provides a flexible platform for differentvoltages based on vertical thickness and/or trench depth. Semiconductordevice 250 containing one or more isolated power devices and associatedcontrol logic can be used in many applications, such as automotive,switch mode power supplies, and diode bridges for sine-waverectification.

FIG. 5 illustrates semiconductor device 250 disposed in split leadframe252 with lead fingers 252 a-252 h. Bond wire 254 is coupled between leadfinger 252 a at the drain of the power MOSFET in power region 140 a tocontrol logic in control region 144 a for drain sensing. Lead fingers252 b and 252 c are coupled by bond wire to control region 144 a andcontrol region 144 b. Bond wire 256 is coupled between lead finger 252 dat the drain of the power MOSFET in power region 140 b to control logicin control region 144 b for drain sensing. Lead finger 252 e is coupledto the source of the power MOSFET in power region 140 a. Lead fingers252 f and 252 g are coupled by bond wire to control region 144 a andcontrol region 144 b. Lead finger 252 h is coupled by bond wire to thesource of the power MOSFET in power region 140 b.

FIGS. 6a-6e illustrate an alternative embodiment of monolithicallyintegrating isolated vertical power devices and control logic on non-SOIsubstrate 258. FIG. 6a shows an N-type base substrate 260 doped withdonor atoms. A P-type EPI layer 262 is grown on base substrate 260. InFIG. 6b , a portion 264 of EPI layer 262 is doped with acceptor atoms toan N-type region as part of the drain connection of a power MOSFET to beformed in power region 140 b. Buried layer 266 is formed in EPI layer262 in control region 144 for isolation and low resistance path. Aninsulating layer 268 is formed over EPI layer 262.

In FIG. 6c , an N-type EPI layer 270 is grown over EPI layer 262. Aportion 272 of EPI layer 270 is doped with donor atoms to form a heavilydoped N-type region as part of the drain terminal of power region 140 b.A portion 274 of EPI layer 270 is additionally doped with donor atoms toform a heavily doped N-type region for an N-well of control region 144.A portion 276 of EPI layer 270 is doped with acceptor atoms for a P-wellof control region 144. Insulation-filled trenches 280 are formed toisolate power region 140 a and 140 b from control region 144. Isolationtrenches 280 form concentric rings around power region 140 a and 140 b,or otherwise extend completely between power region 140 and controlregion 144. Insulation-filled trenches 282 and 284 are formed tolaterally isolate N-well 274 and P-well 276.

Gate structures 290 for power MOSFETs are formed within power regions140 a and 140 b, similar to FIGS. 3a-3h . High voltage terminationtrench 292 is formed around gate structures 290, similar to FIG. 2l .MOSFETs in control region 144 and doped regions of power regions 140 aand 140 b, similar to FIGS. 4a -4 f.

In FIG. 6d , an interconnect structure 300 includes conductive vias 302formed through insulating layer 304 to connect to control logictransistors formed in control regions 144. Conductive layer 306 isformed over insulating layer 304 and conductive vias 302. Insulatinglayer 308 is formed over conductive layers 306 and insulating layer 304.Additional insulating layers like 310, conductive layer 306, andconductive via 312 can be formed for electrical interconnect androuting.

Conductive plug 314 operates as a front-side source contact throughconductive vias 302 to the power MOSFET in power regions 140 a and 140 band is configured for a leadframe to be coupled to the source of thepower MOSFET by a clip, bond wire, or other appropriate mechanism. Draincontact 346 can be routed by bond wire or clip to the top surface ofsemiconductor device 340, e.g. for drain sensing. Conductive layer 316routes electrical signals from the control logic in control regions 144a and 144 b to contact pads for connection to the leadframe by wirebonding or other appropriate connection method. Insulating layer orencapsulant 320 is formed over conductive layer 316 and conductive plug314 for environmental protection and structural integrity. An opening isetched through insulating layer 320 to expose conductive plug 314 andcontact pads of conductive layer 316 for subsequent interconnect.

In FIG. 6e , semiconductor device 340 is shown inverted to form trench342 using a backside etch, e.g. plasma etch. Trench 342 electricallyisolates the drain terminal of a power MOSFET in power region 140 a fromthe drain terminal of a power MOSFET in power region 140 b. Trench 342is formed extending to trenches 280 to complete the lateral isolationbetween power region 140 and control region 144. Trench 342 follows thepath of trenches 280. In one embodiment, trench 342 and trench 280extend completely around each power region 140. In combination, trench342 and trench 280 extend vertically completely through the die forcomplete isolation between control region 144 and power region 140. Insome embodiments, trench 342 extends completely across control region144 such that base substrate 260 and EPI layer 262 are completelyremoved within the footprint of control region 144. An insulating orpassivation layer 344 is formed over base substrate 260 and into trench342. Drain contact 346 is formed over base substrate 260 for backsideinterconnect.

Semiconductor device 340 combines one or more power devices and controllogic fully isolated (source, drain, and gate of power MOSFET andcontrol logic) in an integrated monolithic semiconductor package usingan SOI substrate or non-SOI substrate. The power devices and controllogic can be lateral or high density vertical trench-based semiconductordevices with vertical conduction path from active surface 110 to backsurface 108 in semiconductor die 102. Conductive layers 306 and 316provide electrical interconnect on a first major surface for controllogic circuits. Conductive layer 314 provides electrical interconnect onthe first major surface for the power MOSFET, e.g. source connection.Conductive layer 346 provides electrical interconnect on a second majorsurface for the power MOSFET, e.g. drain connection. The drain of thepower MOSFET can be routed to the first major surface for drain sensingby the control logic, see FIG. 5. Semiconductor device 340 provides aflexible platform for different voltages based on vertical thicknessand/or trench depth. Semiconductor device 340 containing one or moreisolated power devices and associated control logic can be used in manyapplications, such as automotive, switch mode power supplies, and diodebridges for sine-wave rectification.

FIGS. 7a and 7b illustrate diode bridge 350 for sine-wave rectification,including diodes 352, 354, 356, and 358, formed in four power regions140. Diode 352 is coupled between conductive layer 360 and conductivelayer 362. Diode 354 is coupled between conductive layer 362 andconductive layer 364. Diode 356 is coupled between conductive layer 364and conductive layer 366. Diode 358 is coupled between conductive layer366 and conductive layer 360.

While one or more embodiments have been illustrated and described indetail, the skilled artisan will appreciate that modifications andadaptations to those embodiments may be made without departing from thescope of the present disclosure.

What is claimed:
 1. A method of making a monolithic semiconductordevice, comprising: providing a substrate; forming an opening extendingpartially through the substrate; forming a semiconductor material withinthe opening; forming a power semiconductor device within thesemiconductor material; forming a control logic circuit in a portion ofthe substrate outside the opening to control the power semiconductordevice; and forming a first isolation trench in the semiconductormaterial to isolate the power semiconductor device and control logiccircuit.
 2. The method of claim 1, wherein the power semiconductordevice includes a vertical power semiconductor device.
 3. The method ofclaim 1, further including forming a second isolation trench in theportion of the substrate outside the opening to isolate a first controllogic circuit from a second control logic circuit.
 4. The method ofclaim 1, further including forming an interconnect structure over thepower semiconductor device and control logic circuit.
 5. The method ofclaim 1, wherein the substrate includes a silicon-on-insulatorsubstrate.
 6. The method of claim 1, further including forming atermination trench in the semiconductor material.
 7. A method of makinga semiconductor device, comprising: providing a substrate; forming apower region in a first portion of the substrate, wherein the powerregion includes a power semiconductor device; providing a control regionin a second portion of the substrate, wherein the control regionincludes a control logic circuit to control the power semiconductordevice; and forming a first isolation trench between the power regionand control region to isolate the control logic circuit and powersemiconductor device.
 8. The method of claim 7, wherein the powersemiconductor device includes a vertical power semiconductor device. 9.The method of claim 7, further including forming a second isolationtrench in the control region to isolate a first control logic circuitfrom a second control logic circuit.
 10. The method of claim 7, furtherincluding forming an interconnect structure over the power region andcontrol region.
 11. The method of claim 7, wherein providing thesubstrate includes forming a silicon-on-insulator (SOI) substrate. 12.The method of claim 11, wherein forming the SOI substrate includes:providing a base substrate; forming an epitaxial layer over the basesubstrate; disposing a wafer over the epitaxial layer; and forming aburied oxide layer between the epitaxial layer and wafer.
 13. The methodof claim 7, further including forming a termination trench in the powerregion.
 14. A semiconductor device, comprising: a substrate; a powerregion formed in a first portion of the substrate, wherein the powerregion includes a power semiconductor device; a control region formed ina second portion of the substrate, wherein the control region includes acontrol logic circuit to control the power semiconductor device; and afirst isolation trench formed between the power region and controlregion to isolate the control logic circuit and power semiconductordevice.
 15. The semiconductor device of claim 14, wherein the powersemiconductor device includes a vertical power semiconductor device. 16.The semiconductor device of claim 14, further including a secondisolation trench formed in the control region to isolate a first controllogic circuit from a second control logic circuit.
 17. The semiconductordevice of claim 14, further including an interconnect structure formedover the power region and control region.
 18. The semiconductor deviceof claim 14, wherein the substrate includes a silicon-on-insulator (SOI)substrate.
 19. The semiconductor device of claim 14, wherein the SOIsubstrate includes: a base substrate; an epitaxial layer formed over thebase substrate; a wafer disposed over the epitaxial layer; and a buriedoxide layer formed between the epitaxial layer and wafer.
 20. Thesemiconductor device of claim 14, further including a termination trenchformed in the power region.